Method of applying a protective and electrically insulating covering to components



United States Patent METHOD OF APPLYING A PROTECTIVE AND ELECTRICALLY INSULATING COVERING TO COMPONENTS William Frank Glover and Frank Ernest Giles, London, England, assignors to International Standard Electric Corporation, New York, N. Y.

No Drawing. Application November 28, 1952, Serial No. 323,142

Claims priority, application Great Britain December 13, 1951 4 Claims. (Cl. 117-113) The invention relates to a process for covering components with an even coating of material to provide protection and electrical insulation.

It is general practice to use paper as an electrical insulating material for many components, and the usual method of covering the components is by wrapping paper in the form of tape around them. There is however difficulty in applying this method with components of various shapes, such for example as toroidal coils.

The object of the present invention is to obtain an even layer of paper on the component by means of a comparatively simple operation. The protective coating obtained has mechanical strength and will protect the article from damage, and also has good electrical insulation properties.

The present invention comprises dipping the component into a dispersion of powdered paper in a volatile medium and evaporating the volatile medium to leave an even coating of paper on the component.

In a particular use of the method the powder used is made from acetylated resinated paper and in the powder described and claimed in British specification No. 553,304 as being used as a moulding powder. The size of the powder particles largely determines the depth of the coa ing, since the coating cannot be less deep than the size of the particles. Therefore to ensure a particular thickness of coating in this case, the powder was passed through a 30 mesh B. S. sieve and then mixed with a suitable liquid. The liquid used was trichlorethylene in the ratio of 530 grammes of powder to 4,505 litres of trichloroethylene. This ratio which is important in order to get the correct viscosity of mixture depends to a large extent upon the size of the powder particles. After stirring the mixture to ensure an even dispersion of the particles the object to be coated was lowered into it and immediately removed and dried in a ventilated oven. Further coatings may then be given if required.

The coating formed is found to be firmly attached to the component, is tough mechanically and a good insulator electrically and the method used although resulting in a finish equal in all respects to the normal paper lapping method has the greater advantage that it produces the result by a comparatively more simple operation.

While the principles of the invention have been described above in connection with specific embodiments and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What we claim is:

1. Method of applying a protective and electrically insulatin covering to a solid electrical component, which method comprises dipping the said component into a dispersion of powdered acetylated paper in a volatile liquid medium to provide a covering of the dispersion upon said component, removing said covered component from said dispersion, and evaporating the volatile medium to leave an even coating of paper on the component.

2. Method as claimed in claim 1 in which the paper has been impregnated with a synthetic resin before being powdered.

3. Method as claimed in claim 2 in which the synthetic resin used is polystyrene.

4. A solid electrical component coated with acetylated paper and prepared in accordance with the method of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 1,675,419 Myers July 3, 1928 2,178,358 Havald Oct. 31, 1939 FOREIGN PATENTS 553,304 Great Britain 1943 

1. METHOD OF APPLYING A PROTECTIVE AND ELECTRICALLY INSULATING COVERING TO A SOLID ELECTRICAL COMPONENTS, WHICH METHOD COMPRISES DIPPING THE SAID COMPONENT INTO A DISPERSION OF POWERED ACETYLATED PAPER IN A VOLATILE LIQUID MEDIUM TO PROVIDE A COVERING OF THE DISPERSION UPON SAID COMPONENT, REMOVING SAID COVERED COMPONENT FROM SAID DISPERSION, AND EVAPORATING THE VOLATILE MEDIUM TO LEAVE AN EVEN COATING OF PAPER ON THE COMPONENT. 